Local production of leukotriene (LT)C4 has been implicated in vasospasm, bronchoconstriction and the regulation of vascular permeability. LTC4 production by endothelial cells (EC) or vascular smooth muscle cells (SMC) in vitro requires an exogenous source of the precursor, LTA4. It has been shown that polymorohonuclear leukocytes (PMNL) can provide LTA4 as substrate for vascular cell LTC4 synthesis. Other data suggests that prostacyclin (PGI2), an EC product, can inhibit PMNL production of LTA4. The platelet/PMNL product, 5(S),12(S)-DHETE, a potent antagonist of LTB4-induced PMNL activation, may also play a role by modulating PMNL adherence to EC. This proposal will relate the biochemical interactions of PMNL, vascular cells and platelets to the control of LT synthesis and their physiologic effects. Studies have been proposed to characterize the synthesis of eicosanoids by each cell-type alone and during coincubations. The importance of PMNL adherence to EC during LTA4 transfer will be examined. The function of PGI2 as a biological regulator of PMNL LT synthesis and existence of a feedback control Toop will be tested. The proposal that LTC4- induced increases in EC permeability modulate PMNL migration across intact EC monolayers will be examined. Studies will measure the production and physiologic relevance of platelet/PMNL cooperative metabolites (e.g. 5(S),12(S)-DHETE and 12(S),20-DHETE). This work will be carried out using cultured vascular cells and freshly prepared human leukocytes and platelets. Most analyses will employ high performance liquid chromatography (HPLC) with methods developed in this laboratory. Data will also be collected by radioimmunoassay, enzyme immunoassay, and by gas chromatography/mass spectrometry. Radiolabelled PMNL will be used for adherence studies. Leukocyte migration studies will be performed in collaboration with Dr. Samuel Silverstein and will use EC monolayers grown on amnion. These novel interactions which provide a source of substrate and biochemical modulation of local vascular LTC4 synthesis are potentially important in the vasoconstriction associated with myocardial infarction, vasospastic angina or of bronchial tone during asthma or acute hypersensitivity reactions. Vascular permeability regulation and control of PMNL migration are critical to vascular homeostasis and to all inflammatory reactions.